In a typical nuclear reactor, the reactor fuel core, comprising rods mounted in modular elongated fuel assemblies located in a cylindrical core barrel that is inside a pressure vessel. In a steam generation system using one of these reactors, water is supplied to the pressure vessel, flows down an annular space between the core barrel and the pressure vessel, reverses direction, and flows upward through openings in the lower core support leading to the reactor core. Filling the space between the reactor core and the barrel, a neutron reflector is supplied with some of this water to cool it. U.S. Pat. No. 4,849,162 shows a reflector design, where a plurality of vertically standing rods extend the length of the core tightly packed together, the space between the rods, providing a uniform water passage through the reflector. The diameter of the rods are selected to provide a specific area passage in order to achieve a specific heat transfer. U.S. Pat. No. 4,701,299 discusses a modular lining around the core, and there a lining consists of assemblies of prismatic shape arranged side by side inside the barrel. The resultant liner consists of modular metal elements "juxtaposed" so that the modular lining occupies virtually all the volume of the annulus around the core.
Each of these techniques relies on a heavy, costly and complex reflector having a considerable number of parts, especially fasteners holding the reflector in the barrel.